smith



A. B. SMITH. wwmm: TELEPHONE SYSFEM.

AF LICAHON FILED JUNE I3. I91?- 1,368,850.

Patented Feb. 15, 1921. i w 2 snzns-snsn 1.

A. B. SMHH. AUTOWIL, TIC TELEPHONE S AWUCMIUN FILED JUNE )3,

YSTENL HrZhLzPEess 52mm Zara-lay Patented Feb.

2 SHEETSSHEET 2- UNITED STATES ARTHUR BESSEY SMITH, or mf'nns'ron, tnntiiiolrt.

'mxc commmr, or cnmnoo, Intimate,

nssmiron TO AUTOMAQLIC unc- A. com'om'rmn on rumors.

immature mnnnnnonn SYSTEM.

1,368,850. Applicltlon am June 18'.

To all whom it our concern: I p

Be it known tint I, An'l'iit'tt BESSE-Y SMITH, a citizen of. the United States of America, and a resident ofiEvanston, county of (look, andState of llliliois,;liave invented certain new and Metal Improvements in Automatic T elephone Systems. ot which the followin is, a epeoifl ation.

y invention reltttes in general to automatic telephone systems. but more articutarly to methods of automatic calling between widely separated automatic exchanges e connected by toll or long distance lines. in this respect the present invention may be considered as an improvement on the invention disclosed in my prior application Serial No. 96. 93.

By the prcseut invcution automatic switches at a distant cxchange may be controlled by impulses of alternating: current, transmitted over a toll line by means of an operations. calling dcvice. and translated into the usual two wire interruptions by a repeatcr located at the distant end of the toll linc. There is no current flow on the toll line during conversation to maintain the conncctiou. but instcad thc repeater is provided with a lut'liiltgrclay which holds the line circuit l'oithe automatic switches closed, except for the momentary operating interruptions- Releasiis accomplished by transmitting alternating currcnt of different frequency over the toll line. tlurepeater at 'the distant end being provided with two tuncd relay bridges. mic of which is responsive to 'opcrating current and the other bein; re-

sponsivc lo relcasinp current to unlock the relay before mentioned to release the automati switchcsf Since the alternating currents employed for operatingand releasing purposes are trans'nuttcd over the talking circuit. it is possible to use my invention in connection with phantom toll circuits. or in conncction with toll lines or phantom lincs upon which simplcx telegraph circuits are superimposed. thercby greatly increasing the eiliciency of a toll line system.

The particular means employed in carry-b ing out my invention will be dcscribcd. and a detailed explanation of the working there of will be given hereinafter. reference bcin" had to the accompanyingilrawings, in which Figures 1 and "2. when taken in order with Indication at letters Pfltellt.

the lines at the endsthe'reof in alihement represent diagrammaticallyqe. complete circult connection between a'calling substlation and la called substation A m a. s tern embodying the principles of m inv tion. Theconriectionhas been established t rough the medium of the cord circuit 0, t @1011 line eo'm risin (conductors and 51, the re Seater (Fig 2), and the conneotbrF.

eferrin I now to Fig. 1 of the drawings, the substation A may be of any suitable or approved type,..and as shown herein 'consists o the usual Icpmmon battery arr ngement in which .the transmitter and rec iver are connected'in series. The line conductors 12 and '13 extend to the exchange where they have allotted to them the usual line and cutotl' relays 2 and 3. the answering jack J. and the line lamp L. I

The cord circuit 0 may also be of any suitable type. As shown herein it comprises essentially a bridgebattery supply relay 5 whichin conjunction with the sleeve relay 7 controls the supervisory lamp L: and the ringing up locking relay (3 which-in conjunction with the sleeve relay 8 controls the supervisorv lamp I Key .K is a ringing key, key K is the usual listening ke while the key K is a combined ringingaiu callin device key. The reference character (l i indicates a callingdevice which may bc of the general type of calling; device disclosed in the British patent to Dicker No. 29,654 of 1910. The impulse springs of the calling dcvice.'however, are so designed that when the calling device is operated they will produce momentary closures of the circuit in which it is included instead of the usual momentarv interruptions.

The toll line 50-51 may be providcd at the exchange in which the line of substation A terminates with the regular multiple jacks one of which is shown at J. Associated with the jack J is shown a drop 20. a visual busy signal .21. and a group of-thrcc relays f which the'rclay 24 is the usual cut o i'clay. whilc relays :22 and 23 are special relays which at the propcr time transmit alternating current over the toll line for re leasing purposcs. The relay 23 also has the function of disconnecting the re )eat'er E.

At the distant exchange the tol line 50-51 is provided with the multiple jack J and Patented Feb. 15. 1921.

um. Serial m. 114,444.

make up a single prising relays 67 the associated drop 52 and visual busy signal The relays 54, 55 and 56 correspond to the relays 22, 23 and 24, respectively, which are associated with the jack J, and need not be again described.

he repeater E, as before mentioned, is capable of transforming alternating current impulses which are received over the toll line into the ordinary circuit interruptions which are commonly used for controlling two wire automatic switches; it comprises a pair of condensers 90 and 91 in the talki'ng circuit, a pair of tuned alternating current relay bridges, and a plurality of re a to 72, inclusive. The functions of these relays will be ex lained in the description of the operation uring the establishment of a connection. One of the alternating current bridges, comprising the alternatin current relay 62, condenser 64, and impe ance coil 66, is tuned to the freqliliency of the generator Gen at the first ex- 0 ange and is "used for controlling the operation of the automatic switches. The other bridge, comprising the'alternating current relay 61, the condenser 63, and the im pedance coil 65 ,is tuned to the frequency of the generator Gen, and has the function of controlling the release. The alternating current relays 61 and 62 are of special de sign and respond to alternating current in the same Way as the ordinary relay does to directcurrent. For-example, the relay 62 attracts its armature once for each impulse of alternating current, but doesnot respond to each separate alternation which goes to current impulse. ,in regard to the current frequencies employed, I

-do not wish to limit myself to any particuproximately 20 cycles although not shown in similar to repeater It has been found in. practice, however, that an o crating curpent of 160 cycles per second wi 1 give good results. The release current'which is produced by the generator Gen may have-a frequency/of 5i) cycles per second. These frequencies are high enough so that no interference will occur, due to the ordinary ringing currents which are preferably of a'frequenc of aper second. he a the toll line ISO-51, exactly the same posltion 1n the drawing, is nevertheless in duplicate. Thus the re eater E in Fig. 1', is in Fig. 2. The generator Genin Fig, 2 corres ends to generator (iron in Fig. 1; and it is to be understood that the. operator at whose position the jack J is located may be provided with a cord circuit similar to the cord circuit 0 and having associated with it a generator of the same'frequency as the generator Gen.

Directly connected with repeater E is lar values.

paratus at both ends 0 shown a connector F which may be ofthe pe of connector switch disclosed in IT'S.

ys com March 13, 1906, to Keith, Erickson, and Erickson; the circuits bein' modified, however, in accordance with 1:5 two wire system of control. A connector switch of the foregoing type may be given access to a Inrality of su scribers lines and is operab e in response to the digits of a called number to establish connection with any one of the lines to which it has access. It will be understood, of course, that a selector switch of any suitable construction may be inserted between the repeater E and the connector F in the usual manner in order to increase the capacity of the system. One of the lines to which the connector F has access is the line which is shown in the drawing as extendin to the substation A. The mechanism indicated by the reference character C is an individual line switch associated with the line of substation A and is provided for the pun ose of extending connection to an idle seector switch when the said line is calling. An individual line switch similar to the one herein shown is disclosed in the atent to Newforth No. 1078,690 granted ovember is, 1913.

Superimposed on the toll line 50-51, I have shown a simplex circuit including the two sides of the toll line in parallel, and the conductors 200 and 201 at opposite ends thereof. These conductors 200 and 201 each terminate in a well known type of quadruplex telegra h apparatus shown herein diagrammatic-tidy and indicated b the reference characters QUAD and Q AD. This equi ment may be used for straight telegrap circuits; or, in case the toll line 50-51 1s a phantom circuit instead of a physical circuit, the polar and neutral sides of the quad may be used as the switch control circuits for the two physical lines, respec tively, upon which the phantom is su rimposed. An arrangement of this character is shown in my prior application Serial No. 86596.

While I have shown throu bout the drawings a plurality of batteries, it is to be under-- stood that there is preferably but one hattcry for each exchange, each having its posh tive pole grounded. In order not [to eucumber the drawings, separate re e nce characters have not been applied to the dividual batteries shown, and to avoid misunderstanding, it will be stated that where in the following description, a circuit is traced to battery it exte'nds to the live or ungrounded pole of one of the exchange batteries. the busy signaling machine Q, which are shown associated with the connector F, are of the well known type and need no detailed description.

he operation of the system can best be understood by describing the roccss of es tablishing a connection and a escription of The ringing equipment IR and Ill) this operation will now be given. For this purpose. it will be assumed that the subscribe at substation desires to obtain a eonnertion with the subscribe at substation. A. this being the complete irenit eonneetion shown in the drawing and previously referred to. l pon the removal of the receiver at substation a eircnit is eompleterl for the line relay 2 thereby causing the illumination of the line lamp Id. In this manner the attention of the operator is attracted and she will respond by inserting the answering end of the cord circuit in the answering jaek J. cirenit is there upon eompleted including the sleeve relay 7 and the eut oll relay il whereby the line relay 2 is diseonneeted and the lamp [1 is extinguisln-d. In addition. the battery supply relay 5 in the cord eirrnit is energized over the. calling subseribens loo u aml prevents the illumination of the supervisory lamp L. The ope 'ator will now throw her listening key 'R in order to obtain from the railing snhseriber the usual information eoncerning thl name and number of the party wanted. ete. Although the operations described in the foregoing are purely manual in their elm 'aeter. it w'll be understood that the exchange may emtain also automatic lines whieh may have arcess to the toll operator through the medium of any wellknown type of automatic switehing meehanism.

Since it has been assumed thae'the de-' sired party is the subseriber at sublimation A in the distant exehange. the operator Will now insert the calling plug of the eord cirruit in the jaek J. the idle or busy condition of the toll line being first determined by testing with the tip of the plug in the usual manner. in the jut-k the following eireuit is estal? lished: ground at (l'. wimling of sleeve relay sleeve of plug. sleeve of jack J. winding of relay .22. and the winding ol relay 23 to battery. Relays 1. 2:2. and 23 are energized over thabove eircuit. the former relay opening the test cireuit extending to:

the operat'ons head set and preparing a loeking cireuii tor relay ti. 'lhe energization of relay '3'. has no immediate ell'e t. helay 23. howeyer. disconnects the eondnetors 27 nd 2a which extend to the re ater li' from the line ronduetor i3 and 2(5. r speetively: and also eloses parallel energizing eircnits for the eut oll' relay 2i and the isual busy signal 21. The. rut-oil: relay. upon energizing. disconnects the drop il The visual busy signal '21 is one of a -pln 'ality of sueh signals located a l dill'erent perators positions whirh are all operated in multiple.

The operator will no throw her calling du iec hey I\"-. thereby bridging the calling ileiiee l and the generator (ien ill series :u'ross the tip and ring strands at the calling end of the cord circuit. The ealling deviee the alternating current relay 62.

When the plug is inserted' ehange. eausing the operation of the alteruating current relay (5:3. It is noted that re.- lay (i2 is connected in bridge of the heavy talking conductors 5'.) and (it) which in turn are i-onneeted by way of normally closed contacts of relay 5-: with the heavy talking eondurtors 57 and 5H. respectively. and the, operation of this relay therefore will be sullieiently obvious. The alternating current relay (ll does not respond at this time be-.

eause the bridge in which it is inelnded is not tuned to the frequency of the generator (len'. Neither does the drop 52 respond, for it is adjusted either by means of a heavy armature or by tuning its eireuit so that; it will be actuated only by low frequency cu!" rents. It should be mentioned also that the eondensers tlo and 91 are of very low capacity in order to prevent leakage of an appreciable amount of eurrent through'the line relay ltltl ot' the connector I.

From the t'oregoing it will be elear that at each elosure at the bridge by the ealling device (D. an impulse of high frequency alternating eurrent is transmitted over the toll line to the distant exehange to operate When the relay (l2 energizes in response to the first eurrent impulse. a cireuit is eompleted for the relay (in as follows: ground at (l. arma ture T6 and its working eontaet. contact 8th spring 82. and the winding of relay (it) to battery. A branch of this circuit extends through the relay 3 to battery. l'pon energizing. relay till completes a locking cireuit t'or itsell as follows: gronndat (PM spring 93. eontat't 92. working eontalt of armature S1. armature S1. spring R2. and the winding of the said relay 6!) to battery. eontinnation oi' the above cireuit may be traced through the euLotl' relay 56 as follows: armature Bl. upper winding of the electropolarized relay T1. armature FT and its resting eoutaet. and the winding of the eut-oll' relay fit: to battery. I'pon energizing. relay ho disconneets the drop 52. A branch of the energizing cireiiit of relay .36 extends through the visual busy signal an and its multiples to battery. there y making the toll line terminating in jack J busy to the operators at the seeond exehange. The upper winding of relay T1 is a piilarizing winding only. and does not have a sultieient number of turns to enable the relay to energize. 'hen the relay tin was energized in muli iple with relay (l9. it established a lock ing eircuit for itself over the following path:

ltlll ground at G, armature 86 and its resting contact, armature 80 and its working contact and the winding of the said relay 68 to battery. A further result of the energization of relay 69 is the closure of the circuit for the line relay 100 of the connector F as follows: ground at G, lower winding of line relay 100, contact springs controlled by the lower armature of relay 106, conductor 74, working contact of armature 84 of relay 69 and the said armature, armature 85 and its resting contact, the lower winding of rela 71, conductor 73, contact s rings controlled by the upper armature o relay 106,

and the upper wfnding of the line relay 100 to battery. non the. closure of theabove circuit,.relay 71 not energized owing to the fact that its two windings are connected in opposition. The line rela 100,'however, attracts its armature and c oses the usual energizing circuit for the slow acting release relay 101. Upon energizing, relay 101 prepares circuits for the vertical and rotary ma nets 107 and 108. i

he foregoing operations have all occurred in response to the energization of the alternatin current relay 62 by the first current impu so received over the toll line. When the current ceases to flow, the rela 62 deenergizes and closes a circuit for re ay 70 as follows: ground at G, armature 76 and its resting contact, working contact of armature 7 9 and the said armature, andithe winding of relay 70 to battery. Upon energizing, re ay 70 opens the. locking circuit of relay 68 at armature 86 and at the same'time closes an energizing circuit for the slow acting relay 72. This latter relay upon energizing, short-circuits the lower winding of the relay 71. Upon the opening of its locking circuit, relay 68 decnergizes and opens the circuit of relay 70, which relay also accordin 'ly dee'nergizes. Inasmuch as armature 85 o relay 70 is included in the circuit of the line relay 100 of the connector F, the momentary energization of the relay 70 which has just been described causes an interruption of the circuit of the line relay. When the relay 62 is energized in response to the next alternating current impulse, and subse uently deenergizes at the end of the impu se, relays 68 and 70 operate as before to produce another interruption of the circuit of the line relay 100. These operations occur quite rapidly and since the slow acting relay 72 receives an impulse at each energization of relay 70, it maintains its armature attracted continuously during a series of impulses to maintain a circuit around the lower winding of relay 71.

As explained, each energization of relay 70 produces an interruption of the circuit of the line relay 100 of the connector F. In response to these interruptions of its circuit,

the line relay 100 is dei nergizcd a number of times, and at each denergization, transmits an impulse from ground G through the slow noting relay 102 and'the vertical magnet 108 to battery, side switch wiper 112 being in its first position. In response to these impulses, the vertical magnet is operated to raise the switch shaft step by step until the wipers I40, 141, and 142 arrive at the horizontal level of bank contacts in which is located the terminal of the line of substation A. The relay 102 is energized in series with the vertical magnet and being slow acting, retains its armature during the series of impulses to close a circuit for the private magnet 110. At the end of the series of impulses, relay 102 and the private magnet 110 denergize, the latter advancing called number, thereby transmitting a sec ond series of alternating current impulses over the toil line and causing a second series of energizations of the alternating current rela Relays 68 and respond as before, t 1e latter relay producing a second series of interruptions in the circuit of the line relay 100 of the connector F. The line relay 100 is accordingly again de'nergized a number of times and now, side switch wiper 112 being in its second position, transmits at each deiinergization an impulse from ground G through the relay 102 and the rotary magnet 107 to battery. In response to these impulses, the rotary magnet is operated to rotate the switch shaft step by step until the wipers 140, 1 11, and 142 arrive at the particular set of contacts in which the line of substation A terminates.

The slow acting relay 102 and the private magnet 110 are energized as before and at the end of the final series of impulses,'assuming that the called line is idle, the pri; vate ma net advances the side switch wipers to thir position. By the advance of the side switch wiper 113 to third position, a circuit iscomplcted for the cut-off winding of the line switch C as follows: round at G", side switch wiper 113 in thir position, private wiper 141,;bank contact 144, and the cut-off winding 145 to battery. By the operation of the cut-off. armature 146 the line of substation A .is cleared of its normal battery and ground connections in the line switch C. As a further result of the advance oi the side switch wipers to third position, a circuit is completed in an obvious manner for the line switching relay 105, which relay is accordingly energized to complete a si aling circuit as follows: ground at G e ringing current generator, contact of interrupter IR, conductor 147,

resting contact of armature 14.8 and the said armature, lower armature of relay 105 and its working contact, line wiper 142 and the bank contact engaged thereby, to and through substation A, returning over the upper line conductor to the bank contact engaged by the line wiper 140, working contact of the upper armature of relay 105 and the said armature, armature 149 and its resting contact, and the lower winding of relay 10+ to batter". By the operation of the ringing interrupter IR, a small booster battery is substituted at intervals for the ringing current generator thereby producing an intermittent operation of the ringer at substation A. The relay 104 is adjusted so that it will not energize when the receiver at substation A is on the book.

The 0 erator at the originating exchange, having nished dialing the wanted number, will now restore her calling device key K to normal position, whereby the calling de vice (TD is made available for use in establishing other connections.

lVhe-n the called subscriber removes his receiver in response to the ringing of his hell, the relay 104 at the connector F is energized and completes a locking circuitfor itself as follows: ground at G, off-normal springs 151 closed at the first upward movement of the shaft), working contact of armature'152 and the said armature, and the upper winding of relay 104 to battery. As a further result oi the energization of re lay 104, the lower winding of this relay and the lead to the ringing equipment are dis connected and the coiled end of the talking circuit ,is finally completed. Current for the transmitter at substation A is supplied through the windings of the answering bridge relay 1% in the usual manner. and the relay 106 is therefore energized to reverse the conductors 73 and 74 as regards their connections to the windings of the line relay 100. The direction of current flow in the lower winding of relay 71 is therefore reversed. and since its two windings now assist each other. the relay 71 is energized. By the operation of relay T1. the low ca.- pacity condensers 90 and 91 are short-circuited at the armatures RT and 88 respectively. The complete talking circuit has now been established and conversation may proceed as desired. the voice currents fol lowing the path shown in the heavy lines.

\Vhcn the subscribers are through talk- 'ing. they will both replace their receivers.

iiy the replacing of the receiver at substation A. the relay 5) in the cord circuit 0 is deencrgized to give the operator a disconnect signal by the illumination of the supervisory lamp L. The disconnection, including the release of the automatic switches at the distant exchange. is accomplished by taking down the cord circuit O. When the calling plug is removed from the jack J. the energizing circuit of the relays 22 and 23 is broken. Since relay 23 is slow acting it will retain its arinatures in operated )osition for an instant after the relay 22 has dei nergized, thereby bridging the generator Gen momentarily across the conductors 25 and 26 of the toll line. It follows that an impulse of alternating current will be transmitted by way of the re ieating coii ii, the toll line conductors 50 am 51, and the repeating coil 1% to the distant exchange, where it serves to operate the alternating current relay 61 connected in bridge of conductors 59 and 60. The alternating current relay 62 does not re spend at this time. Upon energizing, rela 61 closes an energizing circuit for rehw ii Relay 67, upon energizing, breaks the ionic ing circuit of relay 6!) and the circuit which includes the upper winding of relay 71 and the cut-oi? relay 5G, and at the same time closes at its armature 78 a circuit .for the cutofl relay n6 which is independent of the re; lay 69. Thus the cut-off relay 56 is maintained energized to obviate anv danger of the dro 52 being actuated by the comparatively ow frequency releasing current. When its locking circuit is opened, relay 69 deenergizes and db its armature 84 opens the circuit of the line relay 100 at the connector F. The dei nergization of relav 100 is followed by the deenergization o the release relay 101, whereupon a circuit for the release magnet 109. is idnsed in the usual manner. By the energization of the release magnet. the connector F is restored to nqrmal, the circuit of the release{;, agnet 09 being broken by the shaft wh I i tdreaches its lowest position. it will be see'n then, that upon the withdrawal of the calling plug of the cord circuit from the jack, an impulse of alternating current of a. lower frequency than the current used for operating purposes is transmitted over the toll line to energize a relay in a tuned bridge at the opposite end thereof, to bring about the release of the automatic switches involved in the connection. it has been assumed in the foregoing explanation, that the line of substation A was idle when called. If this line had been busy. the test relay 103 would have energized in series with the private magnet lit) at the end of the final series of impulses, in order to prevent the completion of the connection to the called line and to transmit a. busy signal from the busy signaling machine Q to the calling subscriber. The low capacity coudensers 90 and 91, which are shunted around the normally open contpcts in .the talking circuit controlled by theirelay 7i, enable the calling subscriber (and the operator if she has her listening key rown) to hear the busy signal. and are provided for this purpose.

in regard to the simplex eiizcnit superimposed on the toll lira, and the quadruplcx apparatus at each end thereof, the use of equipment of this character for telegraph circuits is well known and will need no detailed explanation. In the case of a phantom circuit, this quadruplex equipment. may be used for automatic switch control circuits associated with the two side lines, in the manner disclosed in my prior a plication Serial No. 86596, previously reiiarred to; while connections over the hanto'm circuit are established and released in accordance with the present invention. I am able therefore, by a combination of the two inventions, to set up coi'inections automatically in either direction over any one or all of three telephone circuits, one of which is a phantom circuit superimposed upon the other two.

Having described my invention what I consider to be new and desire to have protected by Letters Patent will be pointed out in the a pended claims.

What claim as my invention is:

1. In a telephone system, an automatic switch, sources of alternating current of alternatin dilferent frequency, and means for operating and releasing said switch by current iinpulses from the said Sources, respectively.

2. In a telephone system, a line tetminat ing in an automatic switch, sources of alter nating current of different frequency, means for controlling the operation of said switch by impulses of current from one of said sources, and means for releasing said switch by an impulse of current from the other of said sources. 3. In a telephone system, an automatic switch, sources of high and low frequency current, means for operating said switc in response to impulses of high fre uency current, and means for releasing said switch in response to an impulse of low frequency current.

4. In a telephone system, a line terminating in an automatic switch, sources of alternating current of difierent frequency, means for connecting said sources momentarily in bridge of said line, a relay associated with said line for controllin the operation of said switch and responsive only to currentof one frequency, and a second relay associated with said line and responsive only to current of a. different frequency to always release said switch. a i

5. In a telephone 'system,a line, a pair of relays associated with said line each responsive only to a particular frequency of alternating current, means for transmitting alternating' currents over said line of the proper frequencies to actuate said relays, an

automatic switch, an operating magnet in said switch under control of one of said re lays, and a release magnet in said switch under control of the other of said relays after a connection is completed.

6. In a telephone system, a trunk line, A.

C. generators of different frequency at one end of said line, a pair of tuned relay bridges corresponding to said generators at the other end of said trunk line, an auto matic switch having an operating magnet under the control of the reiay in one of said bridges, and a release magnet for said switch under control of the relay in the other of said bridges to release said switch at any time during the established connection.

7, In a telephone system, a trunk line, A. (I. generators of different frequency at one end of said line, a pair of tuned relay bridges corresponding to said generators at the other end of said trunk line, an automatic switch having an operating magnet under the control of the relay in one of said bridges, a release magnet or said switch under control of the relay in the other of said bridges, means including a calling device for transmitting current impulses from one of said generators over said line to operate said switch to establish a connection, and means for transmitting an impulse from the other of said generators over said line to accomplish the release.

8. In a telephone system, a line terminat ing in an automatic switch, a repeater in said line, means of alternating current of a certain frequency over said line to operate said switch through the medium of said repeater, and means for transmitting an impulse of alternating current oi different frequency over said line to release said switch through the medium of said repeater.

9. In a telephone system, a line extend ing through a repeater to an automatic switch, sources of alternating current of different frequency, means insaid repeater responsive to current impulses from one of said sources for operating said switch, and means in said repeat-er responsive to a current impulse from the other source for re leasin said switch.

10. n a telephone system. a line extending through a repeater to an automatic current of nism in said switch controlled by one of.

said relays, and release mechanism in said switch controlled by the other of said relays.

12. In a telephone system, a line extendi'or transmitting impulses ing by way of a repeater to an automatic switch, condensers in the line conductors at said repeater, normally open control circuits incoming to said repeater and switch, respectively, mraus for transmitting a series of impulses of alternating current over one of said circuits to said repeater, and means in said repeater responsive to the first of said impulses for closing the control circuit to said switch and for producing a momenta? interruption therein, and responsive to eaci subsequent impulse of the series for, producin anothormomentary interruption therein.

%3. In a telephone system, a trunk line, a source of alternatin current in a normally open bridge of said me at one end, a calling device adapted when operated to produce a series of closures of said bridge to transmit a series of current impulses over said line, and an automatic switch at the other end of said line responsive to said impulses to establish a conneo tion, each impulse of current consisting of a plurality of c cles of alternating current.

14. In a telephone system, a trunk line a source oi. altcrnatin current inn norma I open bridge of said i no atone end, a calling device adapted when operated to produce a series of closures of said bridge-to transmit a series of current impulses over said line, an automatic switch at the other eiid of said trunk line and a local control circuit therofor, said switch being operative responsive to interruptions of its control circuit, and a repeater adapted to produce an interruption in said control circuit in response to each.

impulse received over. said trunlc'line, each impulse of current consisting of a plurality of cycles oi: alternating current.

l 15. In a telephone system, a trunk line, a SUnpleX c11 -cuit..superimposed on sa d line and including the-two sides thereof in par allel, direct currentapparatus for operation over said simplex circuit, an automatle switcluand-means for operatin andreleasing said switch by impulses o alternating current transmitted over the metallic circuit progressively movable including the two sides of said trunk line in series.

16. In a telephone system, a trunk line conncrting two exchanges having a simplex circuit superimposed on said trunk line, which is provided with quadruplex equipment at each end thereof, operated from sources 01" direct current for controlling a pair of control circuits, one control. circuit comprising the polar side and the other comprising the neutral side of said quadruplcx cquipmcl'lt, an automatic trunking switch, a third control circuit comprising the two sides of said trunk line in series for controlling said automatic switch, and means for including a source of alternating current in said third control circuit to control said automatic switch to extend a connection.

17. In a telephone system, an automatic switch, a trunk line leading to said switch terminating in. a jack, :1. source of alternating current, a. plug ending operators cord circuit, said plug adapted to be inserted in said jack and having means associated therewith controllod by the operator for operating said switch to extend a. connection from said trunk line, and means responsive to the removal of the plug from said jack for automatically connecting said source of current to said trunk line to release said automatic switch.

.18. In a telephone system, an automatic switch, a trunk line leading thereto terminoting, in a. jack at the operators position. a source oi alternating current, a nick and a slow relay associated with saic jack, a plug for said operator for insertion in said jack, and means associated with the jack for operatin the switch to extend a connection from the trunk line, said relays responsive to the removal of the plug from the jack-for connecting said source of alternating current to the trunk line momentarily to release said connection.

Signed by me at Chicago, Cool: county, State of Illinois this 8th day of June, 1.9.17.

' ARTFIUR BESSEY SMITH. 

